The overall goal of our research is to better understand the role of LDL oxidation in atherogenesis. Specifically, we wish to define the mechanisms responsible for the documented poor processing of oxidized (ox-) LDL in macrophages. Our working hypothesis is that such deficient processing of apo B by proteases and cholesteryl esters by acid cholesterol ester hydrolase (ACEH) is the result of substrate modification,and/or enzyme inactivation by ox-LDL. We will test this hypothesis by assessing the ability of LDL oxidized to increasing degrees and ox-LDL isolated from human atherosclerotic lesions to be degraded by lysosomal proteases and ACEH within mouse peritoneal macrophages (MPM) and in cell-free systems. We will define the modifications in apo B and cholesteryl esters responsible for their poor degradation using model systems. We will also determine whether ox-LDL can induce the inactivation of protease and ACEH in MPM, and, if so, define the underlying mechanism. We will assess the 'ability of different products derived from the oxidation of LDL to induce such inactivation. Collectively, these studies should enable us to evaluate the contributions of these mechanisms to the poor processing in macrophages of ox-LDL. Better understanding of such specific mechanisms will allow us to better evaluate why ox-LDL is atherogenic and ultimately permit us to develop strategies to reduce these events.